1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, a method of processing a substrate and a substrate processing apparatus.
2. Description of the Related Art
A flash memory includes an electron accumulation region (floating gate) surrounded by an insulating film and operates in a manner such that information is written in the flash memory by exchanging electrons through a thin tunnel oxide film and the stored information is retained for a long time by holding electrons using the insulating capacity of the thin tunnel oxide layer. Such a flash memory is required to retain the stored information for a long time, for example, even 10 years, without requiring any external operation, and thus stricter requirements are imposed on an insulating film surrounding a charge accumulation region which is called a floating gate. A stacked structure of oxide film (SiO2)/nitride film (Si3N4)/oxide film (SiO2), which is generally called “ONO” structure, is used as an interlayer insulating film between a floating gate and a control gate configured to control the operation of a memory cell, and it is expected that the ONO structure has high leak current characteristics.
In a conventional art, SiO2 insulating films of an ONO stacked structure are formed at a high temperature close to 800° C. by a chemical vapor deposition (CVD) method, for example, using SiH2Cl2 gas and N2O gas. However, as the structure of a device becomes finer, the capacitance of a nitride film of an ONO stacked film is decreased, and thus the use of a high dielectric constant film instead of a nitride film is considered to guarantee capacitance. A SiO2 insulating film on a high dielectric constant film is required to be formed at a temperature lower than a temperature at which the high dielectric constant film is formed so as to prevent crystallization of the high dielectric constant film.    [Patent Document 1] Japanese Patent Application No. 2009-178309
When a SiO2 insulating film is formed, if the film-forming temperature is low, the growth rate of the film (film-forming rate) tends to decrease. Therefore, inorganic or organic sources which are highly reactive and are easily adsorbed on a substrate are used. However, since such sources are less available and expensive as compared with conventional source materials, if semiconductor devices are formed by using such sources, the prices of the semiconductor devices may be increased. In addition, if such sources are used, it is difficult to guarantee the thickness uniformity of an insulating film.